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Abstract:

Spacer compositions and products may include a biopolymer component, a
plant fiber component, and a weighting agent component, and in further
non-limiting embodiments may include xanthan gum, a blend of plant
fibers, and a weighting agent component. These spacer compositions and
spacer products may be utilized in well fluid operations, including well
cementing operations and well completion operations.

7. A method of operating a well comprising, adding a spacer product to
the fluid in the wellbore, the product comprising: an aqueous component;
a polymeric component; a fiber component; and, a weighting agent
component.

8. The method of claim 7, wherein the polymer component is a biopolymer
and the fiber component is a plant fiber.

9. The method of claim 7, wherein the biopolymer is a polysaccharide, and
the plant fiber is a plant fiber blend.

10. A well comprising a fluid in the wellbore, the fluid comprising: an
aqueous component; a polymeric component; a fiber component; and, a
weighting agent component.

11. A well of claim 10, wherein the polymer comprises a biopolymer, and
the fiber comprises plant fiber.

12. The well of claim 11, wherein the biopolymer comprises polysaccharide
and the plant fiber comprises a plant fiber blend.

Description:

RELATED APPLICATION DATA

[0001] This application claims priority of U.S. Provisional Patent
Application No. 61/448,185, filed Mar. 1, 2011, the specification of
which is incorporated herein.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to spacer fluid compositions, spacer
fluid products, methods of well operation and well apparatus. In another
aspect, the present invention relates to non-invasive (i.e., minimal loss
to formation) spacer fluid compositions, non-invasive spacer fluid
products, methods of well operation and well apparatus. In even another
aspect, the present invention relates to cement spacer compositions,
cement spacer products, methods of cementing wells, and hydrocarbon well
apparatus. In still another aspect, the present invention relates to
completion spacer compositons, completion spacer products, methods of
well completion, and well apparatus.

[0004] 2. Brief Description of the Related Art

[0005] In the drilling and completion of an oil or gas well, a cementing
composition is often introduced in the well bore for cementing pipe
string or casing in a process known as primary cementing. In primary
cementing, a cementing composition is pumped into the annular space
between the walls of the well bore and the casing. The cementing
composition sets in the annular space, supporting and positioning the
casing, and forming a substantially impermeable barrier/mass or cement
sheath. An essential function of cementing is to prevent fluid exchange
between the different formation layers through which the hole passes and
to control the ingress of fluid into the well, in particular to limit the
ingress of water. In production zones, the casing, the cement and the
formation are all perforated over a depth of a few centimeters.

[0006] "Associative Polymers for Invasion Control in Water- and Oil-based
Mudsand in Cementing Spacers Laboratory and Field Case Histories", Reid
et al., AADE-04-DF-HO-3, discloses that it has long been recognized that
it is very desirable to minimize the invasion of drilling fluids,
completion fluids, workover fluids and cements into subsurface
formations. Further discloses that fluid invasion during drilling and
completionoperations causes many of the biggest problems faced in well
construction. Even further discloses that in the payzone, invasion can
produce formation damage as well as affect the quality of log information
and fluid samples.

[0007] The prior art is replete with many disclosures of cementing in
wells penetrating subterranean formations. In such operations, drilling
fluids (often referred to as "muds") are normally present in oil and
other similar wells at the time of cementing a casing into a borehole
with an aqueous cement slurry. Since the mud and cement are not always
compatible with each other, it is often desirable to separate or prevent
contact between them by use of a cement spacer system. Without the use of
such spacer systems, the incompatibility of the aqueous cement slurry
with the oil based mud is often of such severity that a mixture of the
two forms an unpumpable mass. Such unpumpable masses may prevent
displacement of at least a portion of the drilling fluid with a cement
spacer system. Spacer systems also serve to water-wet the wellbore
surfaces to promote bonding of the cement sheath to the wellbore and
casing. Such cement spacer systems are often thought of as flushing
agents.

[0008] In a typical operation, the cement spacer system is prepared at the
site of entry into the well bore such that the density of the system
matches or exceeds the densities of the fluids to be removed from the
well and the like. In some commercial embodiments, mixing equipment for
such applications may take the form of a 50 to 100 barrel "batch mixer"
or be mixed "on the fly". Some batch mixers may be hydraulically powered,
self-contained unit that mix the cement spacer formulation immediately
prior to the cementing operation. Such units are equipped with large
paddles to facilitate the mixing of the cement spacer, centrifugal pumps
for circulation of the spacer within the batch mixer and pressurized bulk
storage tanks for the transport of the weighting agent for the cement
spacer. Batch mixers may be truck-mounted or skid mounted depending on
wellsite location requirements.

[0009] Once at the drilling site, the spacer system must be prepared from
its constituent materials (typically water, gelling agent and weighting
agent) and combined with any additional materials (such as surfactants or
mutual solvents). The cement spacer system must then be tested for the
appropriate density, with the density adjusted to fall within the
appropriate range for the particular well bore. Independent of the
particular chemistry of the cement spacer system, the storage time of the
finished spacer prior to pumping into the wellbore is generally limited
due to gravitational settling of the weighting agent.

[0010] U.S. Patent Application Publication No. 20100243236, published Sep.
30, 2010, by Koons, discloses nanoparticle-densified Newtonian fluids for
use as cementation spacer fluids and completion spacer fluids in oil and
gas wells. The publication discloses methods for densifying cement spacer
fluids for use in conjunction with drilling fluids and cement slurries
for cementing operations involving oil and gas wells, wherein such
densifying is done via the addition of nanoparticles to the spacer fluid.
Also disclosed are analogous methods of densifying completion spacer
fluids using nanoparticles, to Newtonian fluid compositions resulting
from any such fluid densification, and to systems for implementing the
use of such compositions in well cementing operations.

[0011] U.S. Pat. No. 7,007,754, issued Mar. 7, 2006 to Fanguy, Jr., et
al., discloses a method of cementing an area of a borehole with aqueous
cement spacer system. The storable cement system comprises a suspending
agent, a cement spacer and water. The composition may further optional
contain a surfactant and/or an organic solvent and/or a weighting
material. The suspending agent is preferably a carrageenan or
scleroglucan. The cement system may be stored for an extended period of
time prior to being interposed between a cement slurry and a drilling
fluid. As such, the aqueous cement system may be made off-site and used
when desired for preventing contact between non-compatible
hydrocarbonaceous and aqueous fluids.

[0012] All of the patents cited in this specification, are herein
incorporated by reference.

[0013] However, in spite of the above advancements, there exists a need in
the art for compositions, products, methods and apparatus for well
operations.

[0014] There also exists a need in the art for compositions, products,
methods and apparatus for cementing wells.

[0015] There even also exists a need in the art for compositions,
products, methods and apparatus for completing wells.

[0016] There still also exists a need in the art for non-invasive
compositions, products, methods and apparatus for cementing wells.

[0017] There yet also exists a need in the art for compositions, products,
methods and apparatus for cementing wells that prevent/reduce and/or
minimize fluid loss.

[0018] There even still exists a need in the art for compositions,
products, methods and apparatus for cementing wells that prevent/reduce
and/or minimize gas displacement.

[0019] These and other needs in the art will become apparent to those of
skill in the art upon review of this specification, including its
drawings and claims.

SUMMARY OF THE INVENTION

[0020] It is an object of the present invention to provide for
compositions, products, methods and apparatus for well operations.

[0021] It is another object of the present invention to provide for
compositions, products, methods and apparatus for cementing wells.

[0022] It is even another object of the present invention to provide for
compositions, products, methods and apparatus for completing wells.

[0023] It is still another object of the present invention to provide for
non-invasive compositions, products, methods and apparatus for cementing
wells.

[0024] It is yet another object of the present invention to provide for
compositions, products, methods and apparatus for cementing wells that
prevent/reduce and/or minimize fluid loss.

[0025] It is even still another object of the present invention to provide
for compositions, products, methods and apparatus for cementing wells
that prevent/reduce and/or minimize gas displacement.

[0026] This and other objects of the present invention will become
apparent to those of skill in the art upon review of this specification,
including its drawings and claims.

[0027] According to one non-limiting embodiment of the present invention,
there is provided a well operation spacer composition comprising a
polymeric component; a fiber component; and, a weighting agent component.

[0028] According to another non-limiting embodiment of the present
invention, there is provided a well operation spacer product comprising
an aqueous component; a polymeric component; a fiber component; and, a
weighting agent component.

[0029] According to even another embodiment of the present invention,
there is provided a method of operating a well comprising, adding a
spacer product to the fluid in the wellbore, the product comprising: an
aqueous component; a polymeric component; a fiber component; and, a
weighting agent component.

[0030] According to still another embodiment of the present invention,
there is provided a well comprising a fluid in the wellbore, the fluid
comprising: a polymeric component; a fiber component; and, a weighting
agent component.

[0031] This and other embodiments of the present invention will become
apparent to those of skill in the art upon review of this specification,
including its drawings and claims.

DETAILED DESCRIPTION OF THE INVENTION

[0032] The spacer compositions of the present invention may include a
polymeric component, a fiber component, and a weighting agent component.
More particularly, the spacer compositions of the present invention may
include a biopolymer component, a plant fiber component, and a weighting
agent component. Even more particularly, the spacer compositions of the
present invention may include a polysaccharide component, a plant fiber
blend component, and a weighting agent component. Even more particularly,
the spacer compositions of the present invention may include a
polysaccharide component, a synthetic fiber component, and a weighting
agent component. Even more particularly, the spacer compositions of the
present invention may include a polysaccharide component, an animal fiber
component, and a weighting agent component. Still more particularly, the
spacer compositions of the present invention may include a xanthan gum, a
blend of plant fibers, and a weighting agent component. Non-limiting
examples of plant fibers include those derived from rice, peanut hulls
and corncobs (beeswings, pith and/or chaff "BPC").

[0033] Suitable fibers, polymers, aqueous solutions, well fluid additives,
and other additives, may be found in any number of patents including U.S.
Pat. Nos. 7,886,823 7,748,455 7,409,990 7,363,976 6,997,261 6,939,833
6,932,158 6,927,194 6,867,170 6,750,179 6,716,798 6,323,158 6,218,343
6,102,121 6,098,712 6,016,879 6,016,871 6,016,869 5,763,367 5,599,776
and/or 5,332,724, all of which are herein incorporated by reference for
all they teach.

[0034] The polymer component of the present invention may be selected to
provide desired rheology, viscosity and/or settling properties. The
polymer may be any suitable polymer as known in the drilling art.
Non-limiting examples include natural polymers such as starch, xanthan
gum, guar gum, and wellan gum, and include modified natural polymers such
as carboxymethyl cellulose (CMC), polyanionic cellulose (PAC),
hydroxypropyl (HP) guar, carboxymethyl (CM) starch, hydroxy ethyl
cellulose (HEC), and include synthetic polymers such as polyacrylates,
polyacrylamide, vinyl copolymer, and styrene copolymer. These polymers
may function as follows, biopolymers, HEC and polyacrylamide as
viscosifiers, CMC, PAC, starch, CM starch and polyacrylates as fluid loss
control agents, and polycrylates, and polyacrylates, polyacrylamides and
various other copolymers for reactivity. In some non-limiting
embodiments, the polymer component may be a biopolymer in general,
modified cellulosoic polymers, polysaccharides, or starches. Any polymer
utilized herein may have surface functionality.

[0035] In general, biopolymers useful in the present invention include
polysaccharides and modified polysaccharides. Non-limiting examples of
biopolymers are xanthan gum, guar gum, carboxymethylcellulose,
o-carboxychitosans, hydroxyethylcellulose, hydroxypropylcellulose, and
modified starches. Non-limiting examples of useful synthetic polymers
include acrylamide polymers, such as polyacrylamide, partially hydrolyzed
polyacrylamide and terpolymers containing acrylamide, acrylate, and a
third species. As defined herein, polyacrylamide (PA) is an acrylamide
polymer having substantially less than 1% of the acrylamide groups in the
form of carboxylate groups. Partially hydrolyzed polyacrylamide (PHPA) is
an acrylamide polymer having at least 1%, but not 100%, of the acrylamide
groups in the form of carboxylate groups. The acrylamide polymer may be
prepared according to any conventional method known in the art, but
preferably has the specific properties of acrylamide polymer prepared
according to the method disclosed by U.S. Pat. No. Re. 32,114 to
Argabright et al incorporated herein by reference.

[0037] The weight ratio of the components of the spacer compositions of
the present invention may generally be as follows: for each 1 lb of
polymeric component, in the range of about 0.5 to 15 lbs fiber component,
and in the range of about 0.5 to 20 lbs of weighting agent component.
Non-limiting examples of suitable weighting agents include clays, barite,
hematite, metal oxides or other dispersed solids. The weight ratio of the
components of the spacer compositions of the present invention may
generally be as follows: for each 1 lb of polymeric component, 0.5, 1, 2,
3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 or 15 lbs of fiber component, and
0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or
20 lbs of weighting agent component. It should be understood that based
on 1 lb of polymeric component, any suitable amounts of fiber component
and weighting agent as shown above may be selected. The density of the
spacer fluid will generally be selected to be less than the density of
the lead cement and yet more than the density of the drilling fluid. In
essence, in the well, the spacer will push the drilling fluid, and the
cement will push the spacer. As a non-limiting example, a cement of
density 14 lb/gal, a spacer of density 13 lb/gal, and a drilling fluid of
12 lb/gal.

[0038] The spacer composition of the present invention may include other
components as desired for the particular well operation. As non-limiting
examples, anti-settling agents, dispersal agents, fluid loss controlling
agents, viscosifying agents, and the like. For aqueous-based spacer
fluids, all of such one or more additional components may be soluble
and/or dispersible in water. Furthermore, in some instances a single
component additive may impart a plurality of properties to the resulting
fluid mixture. Such optional components my be present (per each 1 lb of
polymeric component) in the range of about 0.5 to about 20 lbs of
optional components, specifically for each 1lb of polymeric component
0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or
20 lbs of optional component.

[0039] As a non-limiting example, the spacer composition may include as a
optional component in the range of about 0.5 to about 8 lbs of FLC 2000
for each 1 lb of polymeric component, more particularly 0.5, 1, 2, 3, 4,
5, 6, 7, or 8 lbs of FLC for each 1 lb of polymeric component.

[0040] FLC 2000® is a fluid loss control and stabilizing agent and is a
high temperature stable dynamic Fluid Loss Control and Borehole
Stabilizing Agent, not affected by borehole contaminants, for water or
oil-based muds. This product converts almost any water and oil based
drilling or workover fluid (including sodium formate) into a non-invasive
fluid. FLC2000 is a precise formulation of fluid loss controlling and
shale stabilizing polymers of varying solubilities, based on surface
chemistry effects to minimize wall cake thickness, reduces differential
sticking, and mechanically stabilize weak sands, shales, and faults, in
either water or oil muds. Both FLC2000 and GSX-305-05 comprise
polysaccharide.

[0042] The non-limiting examples are provided merely to illustrate
non-limiting embodiments of the present invention. These examples are
formulated for mixture with 42 gallons of fresh water, although they
could be mixed with any suitable number of gallons of any suitable
aqueous component.

[0044] A specific non-limiting example of a spacer composition of the
present invention comprises: [0045] 1.0 lbs of high molecular weight
xanthan biopolymer (a suitable polymer for all these examples includes
KELZAN® XCD available from Kelco Oil Field Group, and it is a
dispersible, high molecular weight Xanthan biopolymer used for rheology
control in water based systems, and is a non-hazardous material and can
safely be used in environmentally sensitive areas.). [0046] 4.0 lbs of
FLC 2000 (from Impact Fluid Solutions is a blend of modified low
molecular weight polymers, surface functionalized organic solids and
other additives that impart ultra-low invasion properties to drilling,
completion and workover fluids). [0047] 2.0 lbs of Ultra Seal® XP (is
a blend of specific micro-sized cellulosic fibers namely rice and corn
materials, combined with a blend of organic polymers and lubricity
enhancers). [0048] 9.0 lbs of Sodium Bentonite.

[0068] The spacer compositions, spacer products, and well operation
methods may prevent filtrate invasion, lost circulation, improve cement
bond and/or prevent gas invasion, during and/or after the particular well
operation.

[0069] Additionally, the spacer compositions, spacer products, and well
operation methods may separate drilling fluid from cement, may clean the
well, may be compatible with both drilling fluid and cement, and/or may
assist in maintaining well control.

[0070] Even additionally, the spacer compositions, spacer products, and
well operation methods may form an impermeable membrane rather than
filter cake. More particularly, the spacer membrane may be sufficiently
strong to prevent loss of whole fluid into a weak formation, the spacer
alone may cure moderate losses, in some instances the addition of fibers
(as a non-limiting example the commercially available Ultra Seal®
Plus) may cure severe losses, the low permeable membrane may inhibits
loss of filtrate from cement during and/or after placement, and/or may
maintains hydrostatic pressure longer during cement's transition time.

[0071] Still additionally, the spacer compositions, spacer products, and
well operation methods may protect the formation from filtrate damage,
may stop volume losses during well operations (for example cementing),
may mitigates gas flow after the well operation (for example cementing),
may be compatible with water base and oil base drilling fluids, including
synthetic oil base drilling fluids (a liquid or dry surfactant or blends
of surfactants may be added to the spacer to make the spacer slurry
compatible with oil base mud), and/or may be weighted up to 19.0 lb/gal
with any suitable weighting agent (non-limiting examples include calcium
carbonate, barite and hematite).

[0072] The primary requirement for cement spacer fluids is that they be
compatible with both the drilling fluid and the cement slurry that they
are used in conjunction with. Additionally, the spacer fluids should
possess certain rheological tendencies, such as turbulent flow at lower
shear rates, which assist in granular solids removal and which encourage
the removal of the drilling fluid filter cake from the walls of the well.
Turbulent flow is generally regarded as the most effective method for
well cleaning during cementing operations, although laminar flow may also
be utilized in some embodiments.

[0073] The density (or weight) of a cement spacer fluid should be variable
and will typically be adjusted according to well control and
compatibility parameters associated with the particular drilling fluid
and cement slurry with which it is associated. In some instances, where
there is a density mismatch between the drilling fluid and the cement
slurry, the spacer fluid is densified such that it is intermediate
between that of the drilling fluid and the cement slurry. Additionally,
the density of the spacer fluid can be graduated to better match the
densities of the fluids between which it is interposed. See, e.g.,
Wilson, U.S. Pat. No. 5,027,900. For turbulent flow, the density of the
cement spacer fluid is typically limited to ˜10 pounds per gallon
(ppg) using traditional densification methodologies (e.g., saturated NaCl
brine).

[0074] Cement slurries are typically more viscous than the drilling fluids
preceding them in a given cement job, and spacer fluids have historically
had viscosities that are typically intermediate to that of the drilling
fluid and cement slurry they are used in conjunction with, wherein the
relatively high viscosity of such spacers generally requires that they be
pumped under laminar flow. The viscosity of the cement slurry is also
largely a function of the various components added thereto. To retain the
desired rheological properties and permit turbulent cleaning of the well,
such spacer fluids should generally have a relatively low viscosity
(e.g., ˜5 centipoise (cP) or less).

[0075] Historically, cement spacers have been densified by adding
viscosifying agents and/or non-soluble weighting agents to fresh water,
seawater, brines, or other aqueous or non-aqueous base spacer fluids
(higher viscosity is needed to support the dispersion of the weighting
agents). The resulting fluids, however, are either high viscosity
Newtonian fluids, Bingham plastic fluids, power law fluids, or modified
Hershel-Bulkely fluids--all of which are incapable of being placed in
turbulent flow, at achievable rates, around the entire annular region.
Accordingly, such fluids must be pumped in laminar flow to maintain well
control and effective cementation of the annular space.

[0076] The spacer compositions and products of the present invention may
be utilized in any well fluid operation, including completion operations
and cementing operations. The spacer compositions and spacer products may
be utilized in wells and well operations in general, more particularly
hydrocarbon wells, oil wells, gas wells, and/or oil and gas wells.

[0077] The present invention is also directed to methods of using such
spacer compositions and/or spacer products in any suitable well
operation, non-limiting examples of which include cementing operations
and completion operations. The present invention is also directed to well
operation methods utilizing the space compositions and/or spacer products
of the present invention, non-limiting examples include methods of
cementing wells and methods of completing wells.

[0078] The present invention is also directed to apparatus comprising a
wellbore comprising a well fluid residing therein comprising the spacer
composition and/or products of the present invention.

[0079] The present disclosure is to be taken as illustrative rather than
as limiting the scope or nature of the claims below. Numerous
modifications and variations will become apparent to those skilled in the
art after studying the disclosure, including use of equivalent functional
and/or structural substitutes for elements described herein, use of
equivalent functional couplings for couplings described herein, and/or
use of equivalent functional actions for actions described herein. Any
insubstantial variations are to be considered within the scope of the
claims below.